From European Patent No. EP 0 869 278, a fuel injector with a controllable actuator is known which is inserted in an actuator housing which is fixedly connected to a valve member. The actuator is in operative connection with a valve needle. Formed on the valve needle is a valve-closure member which cooperates with a valve-seat surface to form a valve-sealing seat. The material of the actuator housing has a thermal expansion coefficient which is nearly equal to the thermal expansion coefficient of the piezoelectric actuator. The actuator housing is inserted in a recess of the valve member and screw fitted to the valve member via a flange which is situated approximately in the middle of the longitudinal extension of the actuator housing. The temperature-related expansion of the actuator and the transmission elements up to the valve-closure member corresponds to the temperature-related expansion of the valve member and the actuator-housing segment, from the flange up to an end element on which the actuator is braced.
Disadvantageous in the described related art is that it is difficult to achieve a sufficiently precise temperature compensation. The temperature expansion is only approximately linear, and the employed piezoceramics of the actuator in part have negative temperature expansion coefficients. Furthermore, it is disadvantageous that relatively large quantities of expensive special materials, such as invar, are required. Also, the actuator housing is not effective for temperature compensation in its entire length, but only between the flange and a contact surface of the actuator.